98 



HALF AN HOUR WITH CORALLINES. 



more or less retained in the word " zoophyte," or 

 animal-plant. In the species of which we are 

 speaking, the cells or calycles end in a sharp point, 

 with a small, intermediate tooth 

 (see Fig. 48, I}. The capsules are 

 large and pear-shaped (Fig. 49), 

 and have a circular hole. 8. oper- 

 culata lives a little below the low- 

 water mark, and is parasitic. 



Every one must have seen the 

 pretty little object which goes by 

 the name of the " Sea-oak Coralline " 

 (Sertularia pumila, Figs. 50, 51). 

 It is of a greenish colour, and occurs 

 Capsule of Sertularia in considerable abundance on the 

 common serrated wrack. Indeed, 

 the latter is often invested with 

 such a quantity of it as almost to 

 have its fronds weighed down with 

 it. The illustration will easily con- 

 vey an idea of how this little zoo- 

 phyte clings to seaweeds, and also 

 give a good notion of what it is like. 

 The shoots are seldom more than 

 half an inch in height, and are 

 threadlike, and very sparingly branched. The hydras 

 inhabiting the cells or calycles, when examined with 

 a strong magnifying glass, are seen to possess four- 

 teen to sixteen tentacles. When these are displayed 

 the hydra usually extrudes its body far beyond the rim 



operculata. 

 Fig. 50. 



Sea-oak Coralline. 



